Boiler furnace wall and part therefor



May 9, 1939.

J. H. LAWRENCE BOILER FURNACE WALL AND PART THEREFOR Filed April 1, 1937 2 Sheets-Sheet l INVENTOR. z//wv LA I/I/FPEA/CE y V 1/ ATTORNEYS y 9, 1939- J. H. LAWRENCE 2,157,904

BOILER FURNACE WALL AND PART THEREFOR Filed April 1, 1937 2 Sheets-Sheet 2 mmmmgm INVENTOR.

cfOH/VHLAWAS CE. fi/z/wvwdg A TTORNEYS Patented May 9., 1939 PATENT orrica BOILER FURNACE WALL AND PART THEREFOR John H. Lawrence, Bronxville, N. Y., assignor to Metropolitan Engineering Company, Brooklyn, N. Y., a corporation ofNew York Application April 1, 1937, Serial No. 134,263

6 Claims.

In boiler furnaces heated by pulverized coal, oil, gas or similar fuel, introduced through nozzle burners, combustion is maintained by supplying air to the jet at successive points of its length within the furnace. This invention provides a furnace wall especially adapted to this purpose. In this connection the invention provides also certain tubular units of a design specially adapted for such furnace walls, and adopted generally for furnace walls.

Fig. 1 is a vertical section of a boiler and furnace illustrating the air inlet wall in section; Fig. 2 is a fragmentary elevation of the inner face of the wall; Figs. 3 and 4 are respectively a horizontal section and a side elevation of a tubular unit used in building the air inlet wall; Figs. 5 and 6, Figs. '7 and 8 and Figs. 9 and 10 are similar views respectively of modified styles of tubular unit; Fig. 11 is a perspective view of another style of unit.

Referring to Figs. 1 and 2, the boiler consists of the overhead tubes II in a usual or suitable arrangement and, beneath them, a combustion chamber with a back wall I2 and front wall l3, the latter being constructed with a number of horizontal air lanes 14. At the top of the furnace there is a series of pulverized coal burners l5 through which the mixture of coal and air under pressure is introduced as indicated roughly at I6.

The inner portion of the front wall I3 is provided with apertures through which air from the lanes I4 is admitted to the jet l6 of fuel to gradually complete combustion to the desired extent.

The inner wall is composed of a numlber of vertical tubes ll spaced apart from each other and connected into the circulation of the boiler by way of top and bottom headers 8 and 9 re- 40 spectively. In the case illustrated they are steam generating tubes. They may be used for superheaters or other auxiliaries. The spaces between the tubes open directly into the air lanes M. In order to limit the admission of air, the tubes are provided with extensions l8 welded thereon and extending to considerable distances: outward therefrom, so that the projections from adjacent tubes taken together practically extend clear across the spaces between them. Two lines of projections are shown, at diametrically opposite points of the tube, and this is sufficient to control the air admission. But the projections have another function, which may be utilized to a fuller extent by providing more than two lines of them.

Projections serve the additional function of constituting extended heating areas of the tubes. They are highly heated by the flames and their heat is conducted to the tubes so as to increase the rapidity of the circulation and the genera tion of steam. To do this effectively they must be united with a good heat conducting joint to the tubes. I propose for this purpose to weld them, preferably by a resistance weld passing through the entire area of contact and thus providing a maximum heat conducting area of homogeneous metal.

It has been found that when welding projections of this sort to the tube, where the welded joint is of considerable length (say above twelve inches) internal strains are set up upon cooling, that tend to crack the tube. Such strains in the projections also render them more liable to corrosion and burning out under high temperatures. By using projections which are small at the welded end, of the order of one inch for ordinary boiler tubing of three or four inches as illustrated, these objections are obviated and they may be made of considerable width (transverse to the tube axis) and still be proof against burning- The space between the projections, longitudinally, may be greater or less according to the requirements of air, and they may vary from the top to the bottom of any line of projections. They may, in fact, after installation, be bent back to provide for greater volume of air admission. They are made of soft steel, or similar metal, and of such small cross-section that they can be readily bent back and forward to determine by trial the best conditions for good operation of the boiler.

According to Figs. 5 and 6, projections I9 are used which are inclined upward to project the air upward against the flow of the fuel jet. According to Figs. '7 and 3, the angle of theprojections 20 is reversed, the air being directed downward so as to more gradually with the fuel. Different directions of the air are utilized in different designs of furnaces. According to Figs. 9 and 10, projections 2| are used which in end View have their greater dimension parallel to the normal flow and a fairly long distance between projections. The frictional resistance is cut down by making the projections of Figs. 6 to 10 of approximately lenticular shape, so as to gradually widen the passageway at the en.- trance and at the exit of the air. In the case of projections arranged as in Figs. 6, 8'and 1i), the cooling effect of the air is greater and the heating effect of the flame less than where the broad side of the projection is exposed to the flame as in Fig. 4.

Fig. 11 illustrates a style of tubular unit which may be used. The projections 2| have reduced rounded ends welded to the tube and have their broader faces parallel to the axis and their edges spaced as closely together as is practicable. As originally built, these units would let in very small quantities of air. It is proposed to set them up in the wall, and then bend some of the projections as indicated at 2| until the air is admitted in the right quantities and locations.

It has been previously proposed to make these air inlet walls of a tube whose flanges are cut away to provide openings and also of separate flange sections of the order of twelve inches or more, lengthwise of the tube. have not been successful, because of the internal strains set up in the welding operation as above. By the use of separate projections, each united through a small welding area to the tube, these difficulties will be avoided and the projections may be made of a width or distance extending beyond the tubes, much greater than was the case in the prior constructions. Where separate projections of substantial length at the welded area have been used, the expansion of the outer, hotter, edges has put such a strain on them as to gradually separate their inner edges from the tube at the ends of the joint. This, of course, diminishes the rate of conduction of heat and has resulted in the burning off of the edges of the flanges. For these reasons, in practice, such flanges can only be made of slight width, and the tubes have had to be too close together for the desired free passage of air, And even with narrow projections there have resulted distortions and cracking of the tubes.

In my present scheme of using a small welded area, the projections can be made of considerable width and the tubes spaced as far from each other as desired. The ends of the projections. are so small that expansion thereof puts no substantial strain on the weld. For example, in the design of Figs. 3 and 4 the width, that is, the outward extension, of the projections is more than twice as great as the length or maximum dimension, of the welded end; in Figs. 5 to 10. about twice as great; in Fig. 11 more than twice as great and in Fig. 2, approximately twice as great, slightly under this figure.

When such tubes are set up as the lining of a boiler furnace, particularly when using powdered coal or other fuel burned in suspension, the radiant heat is very great. To prevent passage of radiant heat between the projections, and for other reasons, it is desirable to cover the spaces between them.

This is accomplished by overlapping them in the vertical direction. For example in Figs. 6 and 8 it will be observed that a horizontal line cannot be passed across any of the spaces between the projections l9 or 28 without cutting one or the other of these projections. Since the radiant heat passes in a straight line from its source, there can be almost no radiant heat passing beween such overlapping projections, as compared with arrangements such as are shown in Figs. 4 and 10.

Various other modifications may be made by those skilled in the art without departing from the invention as defined in the following claims.

What I claim is:

1. A furnace for boilers and the like having nozzle burners and a wall along which the stream But these schemes of fuel is directed, said wall comprising tubes in the circulating system of the boiler, said tubes being spaced apart and each of said tubes having a line of projections welded to it at separate points and extending toward the adjacent tubes, the spaces between the projections in line being in communication with a supply of air for combustion, whereby the air is admitted through a number of openings along the height of the wall and is fed gradually to the stream of fuel, the spacing of the tubes being comparatively great and each of said projections extending outwardly for a distance which is at least about twice as great as the dimension parallel to the axis of the tube so as to avoid production of internal strains and to permit such great width and tubespacing without danger of burning off the ends of the projections.

2. A furnace for boilers and the like having nozzle burners and a wall along which the stream of fuel is directed, said wall comprising tubes in the circulating system of the boiler, said tubes being spaced apart and each of said tubes having a line of projections extending toward the adjacent tubes, the spaces between the projections in line being in communication with a supply of air for combustion, whereby the air is admitted through a number of openings along the height of the wall and is fed gradually to the stream of fuel, the projections having in end view their greater dimension parallel to the flow of air between them so as to get a comparatively great cooling effect of the air with a comparatively small surface exposure to the flame and having their rear and front edges reduced in thickness so as to leave passageways between said projections which are widened at the entrance and exit so as to facilitate the air flow.

3. A furnace for boilers and the like having nozzle burners and a wall along which the stream of fuel is directed, said wall comprising tubes in the circulating system of the boiler, said tubes being spaced apart and each of said tubes having a line of projections welded to it at separate points and extending toward the adjacent tubes, the spaces between the projections in line being in communication with a supply of air for combustion, whereby the air is admitted through a number of openings along the height of the wall and is fed gradually to the stream of fuel, said projections having in end view their greater dimension parallel to the flow of air between them so as to get a comparatively great cooling effect of the air with a comparatively small surface exposure to the flame.

4. A furnace for boilers and the like having nozzle burners and a wall along which the stream of fuel is directed, said wall comprising tubes in the circulating system of the boiler, said tubes being spaced apart and each of said tubes having a line of projections welded to it at separate points and extending toward the adjacent tubes, the spaces between the projections in line being in communication with a supply of air for combustion, whereby the air is admitted through a number of openings along the height of the wall and is fed gradually to the stream of fuel, said projections having in end view their greater dimension parallel to the flow of air between them so as to get a comparatively great cooling effeet of the air with a comparatively small surface exposure to the flame, the opposed faces of adjacent projections being inclined so as to form air passages at an oblique angle to the face of the wall.

5. A tube of the character described having a number of projections thereon welded thereto and extending outward to a substantial distance, arranged in line with and spaced apart from each other, said projections having small welded ends, of less length (parallel to the axis of the tube) than the outward extension of the projections, so as to avoid production of internal strains and to permit comparatively great outward extension of projections and tube spacing without danger of burning off the ends of said projections, said projections also having their adjacent edges overlapping.

6, A furnace wall including a number of parallel spaced tubes with projections thereon welded thereto and extending outward into the space between, said projections having small welded ends, of less length than the Width of the projections, so as to avoid production of internal strains, said projections being in a line with and spaced apart from one another with the edge of one overlapping that of the next.

JOHN H. LAWRENCE. 

